It is uncommon for procedure requests to specify details such as who the anaesthesiologist or scrub nurse or other roles would be - or even who should assist. Instead, if anyone is requested, it's just the primary performer. On the other hand, for performed procedures, capturing everyone who was involved and what they did is typical. If there's a desire to capture the nuances of who should do what on a ProcedureRequest, this can be done with an extension.